For me, one killer is more likely, not because the Tabram murder evidence points one way or the other in isolation, but when considered in a series, it becomes clearer. We have already provided plenty of reasons to consider Tabram to be a Ripper victim, with the only substantive objection being the way the murderer changed the way he used his knife.
It seems you lean towards the single killer because you have decided Tabram was killed by JtR?
Maybe it's easier to accept the soldiers theory if we reject Tabram as a Ripper killing. I just don't agree about there being "plenty of reasons" for having her as a Ripper victim.